Optical unit for optically scanning an information surface, and optical scanning arrangement including the optical unit

Abstract

An optical unit (1) is provided for optically scanning a surface, particularly an information surface of a recording medium (9). The unit comprises a frame (13), a radiation source unit (15), a rotatable mirror unit (17), and an objective system (19) for forming a scanning spot on the information surface, which objective system has an entrance pupil (19b) and an optical axis (19a). From an optical point of view, the rotatable mirror unit is situated between the radiation source unit and the objective system, suspension means being provided for movably supporting the objective system relative to the frame. The suspension means allow a longitudinal movement of the objective system along the optical axis and a pivotal movement of the objective system about a pivot which coincides with the point of intersection of the optical axis and the entrance pupil. Actuating means drive the objective system in accordance with these movements.

I claim: 
     
       1. An optical unit for optically scanning a surface, which unit comprises a frame, a radiation source unit, a rotatable mirror unit, and means for forming a scanning spot on the surface, characterised in that the means for forming the scanning spot include an objective system having an entrance pupil and an optical axis, the rotatable mirror unit being situated, from an optical point of view, between the radiation source unit and the objective system, suspension means being provided for movably supporting the objective system relative to the frame, which suspension means allow a longitudinal movement of the objective system along the optical axis and a pivotal movement of the objective system about a pivot which at least substantially coincides with the point of intersection of the optical axis and the entrance pupil, and an actuating means being provided for driving the objective system in accordance with said movements. 
     
     
       2. An optical unit as claimed in claim 1, characterised in that the suspension means include a first suspension unit situated near the entrance pupil, a second suspension unit which, viewed along the optical axis, is remote from the entrance pupil, which suspension units connect the objective system to the frame and allow the longitudinal movement of the objective system and a pivotal movement of the objective system about a pivotal axis disposed transversely of the optical axis and at least substantially in the entrance pupil. 
     
     
       3. An optical unit as claimed in claim 2, characterised in that the actuating means are electromagnetic means comprising an electric coil unit and a permanent magnet unit, one of said units being secured to the objective system and the other one of said units being secured to the frame. 
     
     
       4. An optical unit as claimed in claim 3, characterised in that the electromagnetic means are spaced from the entrance pupil. 
     
     
       5. An optical arrangement including the optical unit as claimed in claim 1 and further including means for moving the surface to be scanned and the optical unit relative to one another. 
     
     
       6. An optical scanning arrangement including the optical unit as claimed in claim 2 and, further including a tape drive unit for moving an optical tape past the objective system of the optical unit, which tape comprises an information surface forming said surface, a part of the optical tape which faces the objective system having a tape transport direction which extends at least substantially perpendicularly to the pivotal axis of the objective system. 
     
     
       7. An optical unit as claimed in claim 1, characterised in that the actuating means are electromagnetic means comprising an electric coil unit and a permanent magnet unit, one of said units being secured to the objective system and the other one of said units being secured to the frame.